If you love Whitewater rafting, then grab on to your oars. This half day trip includes about 8 class III-IV rapids such as Sunshine Falls and Sledgehammer. The rapids are in the first three quarters of the trip. You can relax of the last half hour as you come out of the Gorge. As a bonus you get some of the most spectacular scenery in Colorado as you wind through the Royal Gorge. You will get the best possible view of Royal Gorge Bridge as you pass beneath it.
The trip from Denver takes about three hours. As an aside you can stop in Canon City, an old Western town just east of Royal Gorge. You might also stay there the night before. We stayed at the Comfort Inn, and made the short journey to the rafting shop both refreshed and excited. To get to the rafting shop, just follow the signs to Royal Gorge Bridge. After you make the right off of US 50, the shop is on the right about a 1/4 mile.
We went in August, and didn't need a wetsuit. Bring tevas or rent booties. You also need to bring sunscreen and a waterproof camera. You can raft from May until August. May is obviously highwater (and you will want a wetsuit, which you can rent).
You can also do a full day trip which I'm sure includes a bunch more rapids. There are tons of rafting shops in the area. We have rafted with performance tours twice, and they did a great job. The other trip we did was the full day at Brown's Canyon in Buena Vista. This trip is also highly recommended. You can get a discount on their website www.performancetours.com
When going home you might be a little adventurous and take the back roads. The coutry is beautiful if you have the time.